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The other day I was looking for example drawings to follow that would be used in a real world context as opposed to basic exercise books and I stumbled across a museum archive of the V2 rocket design. Aside from it being German language the first couple of drawings I opened at random seemed to be very well aligned for what I was looking for and I have started drawing up parts in Inventor.

In the following drawing 361D I got a little confused.

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In part 1 The vertical shaft that extends through the top does not show any signs of threading in either of the sections cuts and I would have assumed that is was a smooth 4.1 dia. drilled hole. However when I look at the Bottom/Top view? I see two concentric circles representing the hole. I thought this represented a threaded hole. Similar the 4 M4 threaded holes in the sides and the 4 M3 threaded holes in the bottom. (M4 represents a 4 mm diameter thread hole?) When I look at the assembly view and section A-B (Above) I noted that part 3 is supposed to pass through the hole in the top of part 1.

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The portion of Part 3 (below) that passes through Part 1 appears to me as it if is a threaded 4 mm diameter shaft due to the M4 designation below it and the double lines for side walls.

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The other shaft that is confusing me is in Part 3 and (above) as well. The threaded hole down from the top is annotated as M4 which I interpreted as a 4 mm diameter hole. According to the assembly drawing section A-B and C-D, Part 4 screws in to this portion of Part 3. Part 4 annotates the shaft as being a matching M4 thread. The confusing part for me is the bottom threaded M4 shaft in Part 3 appears to be wider than the threaded M4 hole above it. Further more the bottom/top view of part 3 seem to indicate that the top threaded hole is a match to the 2 mm dia. transverse through hole at the the bottom of the M4 hole.

Am I misinterpreting something here or are these a drawing errors?

I can't really ask the designer what the correct interpretation should be.

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  • $\begingroup$ looks like the ⌀4.1 hole, in figure 1, is a (close) clearance hole for the M4 screw. The dashed-line concentric circle in the overhead view you're referring to might be a hidden line of a slight countersink (edge break), rather than a thread indication. This makes sense too, because the part in figure 5 is obviously threaded in its center hole and is acting like the nut for the M4 screw fastening the part discussed above. $\endgroup$
    – Pete W
    Commented Nov 3, 2021 at 0:30
  • $\begingroup$ the female thread in part 3 and the male thread on part 4 do look like very much like 2mm diameter, from the scale $\endgroup$
    – Pete W
    Commented Nov 3, 2021 at 0:33
  • $\begingroup$ @PeteW Thank you. I thought the same thing about a potential counter sunk head in Part 1 due to the 4.1dia. dimention not lining up with the hole sides. If that was the case though I could not figure out was the main hole diameter was supposed to be. $\endgroup$
    – Forward Ed
    Commented Nov 3, 2021 at 11:26
  • $\begingroup$ Yes it looks inconsistent in some places. The view showing assembly shows that the male thread on part 3 goes into that "4,1" hole so it must be clearance for that, unless its some self-tapping thread in a softer material, but there's no indication of that $\endgroup$
    – Pete W
    Commented Nov 3, 2021 at 23:03

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